Not sure about the truck back glass but the car weatherstrip has a channel for the glass and a lip that fits over the flange that runs the circumference of the window opening. If you're not going to try to save the old weatherstrip you'll probably have to cut it out. If you've not done one before and aren't sure how it's installed you'll be ahead to at least call and talk with a glass pro.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.